The invention relates generally to systems and methods for dispensing fluids onto moving substrates, and more particularly to adhesive dispensing nozzle configurations for dispensing adhesives in partial spray patterns for partially covering a substrate, and still more particularly to meltblown adhesive dispensing systems including a manifold that supplies adhesive to a plurality meltblowing die assemblies configured for partially covering a substrate with adhesive.
The application of adhesives onto moving substrates is known and has many applications. Adhesives are used, for example, to bond overlapping substrate layers in the production of a variety of bodily fluid absorbing hygienic articles, including disposable diapers and incontinence pads, sanitary napkins, patient underlays, and surgical dressings. Known systems include generally a plurality of adhesive dispensing spray nozzles arranged in one or more arrays extending across a moving substrate for applying an adhesive layer or film thereon. Other systems include one or more die assemblies having a plurality of adhesive dispensing orifices arranged in an array, wherein the die assemblies are sometimes arrangeable side by side to extend the array lengthwise. U.S. application Ser. No. 08/843,224 entitled "Improved Meltblowing Method and System" filed 14 Apr. 1997 discloses a plurality of meltblowing die assemblies, or nozzles, mountable side by side on one or both ends of a common manifold, or head, which provides a metered supply of adhesive to each die assembly. The die assemblies each comprise a plurality of substantially parallel plate members forming an array of adhesive dispensing orifices on a dispensing surface thereof. The array of fluid dispensing orifices of each die assembly compose a section of a longer array formed by the plurality of adjacent die assemblies disposed along a common end of the manifold. One or both sides of the manifold may be mounted adjacent the side of a similarly configured manifold to form still longer arrays of fluid dispensing orifices, thereby providing a modular meltblowing adhesive dispensing system that accommodates substrates having any dimensional width.
In some adhesive dispensing applications, the adhesive is applied to cover the full width of the substrate, and in other applications it is desirable to apply the adhesive to cover only select portions of the substrate leaving other portions thereof without adhesive coverage. In the manufacture of bodily fluid absorbing hygienic articles, for example, it is desirable to form different sized areas of adhesive non-coverage, which may correspond to cut away areas thereof or may be designated for insertion of an elastic band. In these and other applications the areas of adhesive non-coverage may be as narrow as one-eighth of an inch or less and may be as wide as one or many inches, depending on the particular application requirements.
In the past, the supply of adhesive from the manifold to one or more die assemblies has been interrupted to provide one or more corresponding gaps in adhesive coverage on the substrate. U.S. Pat. No. 5,421,941 entitled "Method of Applying an Adhesive" issued on 6 Jun. 1995 to Allen et al. among related patents, for example, disclose a common manifold for selectively intermittently supplying adhesive to a series of meltblowing die assemblies mounted thereon. In FIGS. 1 and 4 of U.S. Pat. No. 5,421,941, the die assemblies are constructed to leave continuous strips of adhesive non-coverage along the length of the substrate, but the particular structure that provides this effect is not disclosed specifically. Notably, in FIG. 2 of U.S. Pat. No. 5,421,941, the side by side arrangement of die assemblies does not provide consistent spacing between the fluid dispensing orifices thereof, evidenced by a gap between the orifices of adjacent die assemblies, suggesting that adhesive coverage on the substrate is not continuous, or at least not uniform, particularly in areas between adjacent die assemblies void of fluid dispensing orifices.
The selective interruption of adhesive supplied to one or more die assemblies to form areas of adhesive non-coverage limits the corresponding gaps or areas of non-coverage to the width of the die assembly to which fluid flow is interrupted, and more generally in proportion to multiples of the spray pattern width corresponding thereto, provided the system comprises several die assemblies having the same width. In U.S. application Ser. No. 08/843,224 entitled "Improved Meltblowing Method and System" referenced above, the meltblowing die assemblies are one inch wide, and generally produce a substantially correspondingly wide spray pattern on the substrate. Thus, interruption of fluid flow to the die assembly or replacement thereof by a blocking plate, which may recirculate fluid back to the manifold, results in an area of adhesive non-coverage approximately inch wide, depending upon the divergence or convergence of adhesive sprayed from adjacent die assemblies.
Some adhesive dispensing manifolds are configured with an array of adhesive dispensing nozzles on opposing end portions thereof, wherein the array of die assemblies on one end of the manifold are offset relative to the array of die assemblies on the other end of the manifold. The offset is usually one-half the width of the die assembly. The gap or area of adhesive non-coverage may thus be reduced to a dimension corresponding to the amount of offset upon interruption of fluid flow to overlapping die assemblies on opposing ends of the manifold. But this approach continues to limit the area of adhesive non-coverage in proportion to multiples of the offset between die assemblies, which is fixed.
Others have suggested rotating or otherwise tilting the manifold relative to the moving substrate to variably reduce the areas of adhesive non-coverage resulting from interruption of the fluid supply or removal of one or more die assemblies from the manifold. This approach however does not provide precise and consistent control of the gaps or areas not covered by adhesive. And, as with the other approaches discussed, does not permit variability among more than one area of adhesive non-coverage, since rotating or tilting the manifold reduces each gap the same extent.
The present invention is drawn toward advancements in the art of dispensing fluids onto moving substrates that overcome problems in the prior art economically.
It is an object of the invention generally to provide novel nozzle configurations for dispensing fluids, and more particularly to provide novel modular meltblown adhesive dispensing systems including a manifold that supplies adhesive to one or more meltblowing die assemblies having various configurations for partially covering substrates with adhesives.
It is a more particular object of the invention to provide novel systems and methods for applying fluids, including fiberized hot melt adhesives, onto substrates from one or more die assemblies mounted on a manifold that supplies fluid thereto. At least one of the die assemblies is selected from a group of die assemblies each having different configurations of fluid dispensing orifices thereon, wherein various combinations of the different die assembly configurations are mountable onto the manifold to provide a wide range of partial fluid dispensing patterns onto the substrate, thereby accommodating any fluid dispensing application.
It is still a more particular object of the invention to provide novel systems and methods for applying fluids, including fiberized hot melt adhesives, onto substrates from one or more die assemblies mounted on a manifold that supplies fluid thereto. The one or more die assemblies are selected from a group of die assemblies having the following configurations generally. A first die assembly configured with a first plurality of fluid dispensing orifices disposed across a left side portion thereof, and with a remaining right side portion thereof void of fluid dispensing orifices. A second die assembly configured with a second plurality of fluid dispensing orifices disposed across a right side portion thereof, and with a remaining left side portion thereof void of fluid dispensing orifices. A third die assembly configured with a third plurality of fluid dispensing orifices disposed across a third intermediate portion thereof, and with remaining right and left lateral side portions thereof void of fluid dispensing orifices. And a fourth die assembly configured with a fourth plurality of fluid dispensing orifices disposed across right and left lateral side portions thereof, and with a remaining fourth intermediate portion thereof void of fluid dispensing orifices.
It is another object of the invention to provide novel systems and methods for applying fluids, including fiberized hot melt adhesives, onto substrates from a plurality of die assemblies mounted on a common mounting surface of a manifold that supplies fluid thereto. It is a related alternative object of the invention to arrange the plurality of die assemblies on the manifold so that the plurality of fluid dispensing orifices of the plurality of die assemblies form not more than a single substantially linear array of fluid dispensing orifices.
It is another object of the invention to provide novel systems and methods for applying fluids, including fiberized hot melt adhesives, onto substrates from one or more meltblowing die assemblies mountable on a manifold. The meltblowing die assemblies each have generally a plurality of fluid dispensing orifices disposed at least partially across a width thereof, wherein any remaining portion of the die assemblies is void of fluid dispensing orifices, thereby forming a partial spray pattern. Each of the plurality of fluid dispensing orifices are flanked by an air dispensing orifice disposed on opposing sides thereof, wherein the air dispensing orifices extend across at least a portion of any remaining portion of the meltblowing die assembly void of fluid dispensing orifices.
It is a further object of the invention to provide novel systems and methods for applying fluids, including fiberized hot melt adhesives, onto substrates from one or more meltblowing die assemblies mountable on a manifold. The meltblowing die assemblies each have a plurality of fluid dispensing orifices disposed at least partially across a width thereof, wherein the fluid dispensing orifices are flanked by air dispensing orifices disposed on opposing sides thereof. At least one of the die assemblies having air dispensing orifices arranged relative to the fluid dispensing orifices to increasingly decrease an oscillation amplitude of fluid dispensed from fluid dispensing orifices approaching an endmost fluid dispensing orifice defining an interface between areas of adhesive coverage and non-coverage on the substrate. It is a related alternative object of the invention to size the fluid dispensing orifices in proportion to the amplitude of fluid oscillation therefrom, whereby the supply of fluid thereto decreases with decreasing fluid oscillation amplitude.
These and other objects, aspects, features and advantages of the present invention will become more fully apparent upon careful consideration of the following Detailed Description of the Invention and the accompanying Drawings, which may be disproportionate for ease of understanding, wherein like structure and steps are referenced generally by corresponding numerals and indicators.